Let's take the compound Sodium Chloride (NaCl)
1. Identify the elements: We have sodium (Na) and chlorine (Cl).
2. Apply rules:
* Rule 1: The oxidation number of an element in its elemental form is always zero.
* Rule 2: Alkali metals (like sodium) always have an oxidation number of +1 in compounds.
* Rule 3: Halogens (like chlorine) usually have an oxidation number of -1 in compounds.
3. Assign oxidation numbers:
* Sodium (Na) has an oxidation number of +1.
* Chlorine (Cl) has an oxidation number of -1.
Therefore, the oxidation numbers in NaCl are +1 for sodium and -1 for chlorine.
Explanation:
Sodium is in group 1, meaning it has one valence electron it readily gives up to achieve a stable octet. Chlorine is in group 17 and needs one electron to complete its octet. When they bond, sodium loses an electron (becoming +1), and chlorine gains that electron (becoming -1).
Key Points:
* Oxidation numbers are a bookkeeping tool to track electron movement in chemical reactions.
* They are not actual charges, but rather a way to represent the hypothetical charge an atom would have if all bonds were ionic.
* The sum of oxidation numbers in a neutral compound must equal zero.
* The oxidation number of an element can vary depending on the compound it is in.
